Disclosed herein are inks with gellants, that can form a gel state, used as receivers for particle materials. The inks are liquid when jetted, but quickly enter a tacky/semi-solid/gel state when cooled below the ink gel temperature on a substrate and prior to curing. Dry powders of various types can be applied to the inks and then can be locked in place when the ink is cured.
Also disclosed herein are methods for producing an image on a substrate using the curable inks as receivers for particle materials.
Magnetic ink character recognition, or MICR, documents and inks are known. Such inks are generally employed in the printing and preparation of security documents, or documents that require a secure feature, such as checks. Conventional ink-jet inks contain a dye or pigment, a solvent system, which may be aqueous or non-aqueous in nature, and may include a combination of solvents or a single solvent, and various other components. These other components may be included to address specific problems relating to ink performance, such as flow characteristics, the ink drying out over time as it sits in the cartridge or when it is deposited on the nozzle during printing, particulate matter in the ink settling out of solution over time, and the like.
Of particular interest are those inks which contain a magnetic pigment or component in an amount sufficient to generate a magnetic signal strong enough to be MICR-readable. Such inks generally fall into the category of magnetic inks in general, and in the more specific sub-category of MICR-readable inks. Using commonly-known thermal ribbon printing techniques, the ink is used to print all or a portion of a document, such as checks, bonds, security cards, and the like; for example, most checks exhibit an identification code area, usually at the bottom of the check. The characters of this identification code are usually MICR encoded. The document with MICR-readable ink is then exposed to an appropriate source or field of magnetization, at which time the magnetic particles accept and retain a magnetic signal. The document can then be authenticated by passing it through a reader device which detects the magnetic signal of the MICR imprinted characters, or “reads” the signal, in order to authenticate or validate the document. Of particular importance in the foregoing is the ability of the magnetic component of the ink to retain a sufficient magnetic signal such that the printed characters retain their readable characteristic and are easily detected by the detection device or reader. The magnetic signal retained by the pigment or magnetic component is known as “remanence”. As might be expected, this characteristic tends to increase with particle size and with the density of the coating of the magnetic pigment.
In the past, thermal ribbon printing mechanisms were used to generate MICR-readable characters or indicia. In this printing technique, the particle size and density of the magnetic pigment or particulate was not a limiting factor because the magnetic component was retained on a ribbon substrate by a binder and/or wax material. Then, upon application of heat and pressure, the magnetic ink was transferred to a substrate. However, the incorporation of such magnetic pigments or particulates into an aqueous or non-aqueous liquid ink presents a new set of considerations. For example, the pigment, which had generally previously been used in the form of pigment or particulate matter of a larger size, exhibited a correspondingly high density, and was thus difficult to maintain in suspension or dispersion within a liquid ink composition. Consequently, it became necessary to reduce the particle size of the magnetic pigment or particulate. However, reducing the particle size brought about a corresponding reduction in the magnetic charge or remanence of the magnetic component. In addition to the foregoing, one wishing to prepare a liquid MICR inkjet ink must also take into consideration the fact that most, if not all, inkjet printers limit considerably the particle size of any particulate components of the ink, due to the very small size of the inkjet print head nozzle which expels the ink onto the substrate.
Piezoelectric inkjet techniques are known, and offer a reliable and cost-effective means of applying digital images. However, inkjet inks and substances capable of being deposited on a substrate through ink jetting currently are required to have a small particle size and a low solid particle content. Large particles and high loadings make it difficult to combine such solid particles to ink jet technology, especially solvent free inkjet applications, as the size impedes normal function of the jetting nozzles and other equipment by, for example, clogging or requiring that their diameter be so large as to prevent accurate printing.
Current MICR technology relies on large particles, microns in length, and high loadings, 25-50 weight percent (wt %), to provide a robust signal for the reader.
Additional similar problems exist with forming an image on a substrate from substances including sizable particles. Image formation with substances having high loading also faces similar difficulties in translation to inkjet technology.
Copending Application U.S. Ser. No. 12/146,967, filed Jun. 26, 2008, the disclosure of which is incorporated herein by reference in its entirety, relates to a MICR inkjet ink comprising stabilized magnetic single-crystal nanoparticles, wherein the absolute value of the magnetic anisotropy of the magnetic nanoparticles |K1| is greater than or equal to 2×104 J/m3. The magnetic nanoparticle may be a ferromagnetic nanoparticle, such as FePt. The ink includes a magnetic material that minimizes the size of the particle, resulting in excellent magnetic pigment dispersion and dispersion stability, particularly in non-aqueous inkjet inks. The smaller-sized magnetic ink particles also maintain excellent magnetic properties, thereby reducing the amount of magnetic particle loading required in the ink.
A need has remained for a method for economically and efficiently allowing incorporation of magnetic or large particles with inexpensive and accurate ink jetting image formation processes.
Copending U.S. Application Publication No. 2007/0123606, the disclosure of which is incorporated herein by reference in its entirety, discloses a phase change ink comprising a colorant, an initiator, and a phase change ink carrier.
Copending U.S. Application Publication No. 2007/0123601, the disclosure of which is incorporated herein by reference in its entirety, discloses a phase change, curable composition comprising a curable monomer, photoinitiator that initiates polymerization of the curable monomer, and a phase change agent that provides the composition with an increase in viscosity of at least four orders of magnitude.
Copending U.S. Application Publication No. 2007/0254978, the disclosure of which is incorporated herein by reference in its entirety, discloses ink vehicles including at least one curable component, and optionally including initiating agents, colorants, non-curable components and other additives.
Copending U.S. Application Publication No. 2004/0018318 discloses a curable coating composition containing at least one component having (meth)acryloyl groups that is polymerized with radiation.
Copending U.S. Application Publication No. 2008/0122914 discloses an ink vehicle including different first and second co-monomers, and a gellant that includes a curable epoxy-polyamide composite gellant.
Copending U.S. Application Publication No. 2008/0000384 discloses a radiation curable phase change ink comprising an ink vehicle that includes at least one curable carrier, at least one gellant, at least one curable wax, and at least one photoinitiator.
Copending U.S. Application Publication No. 2007/0120921 discloses a radiation curable phase change ink including at least one curable epoxy-polyamide gellant and at least one colorant.
Copending U.S. Application Publication No. 2007/0120908 discloses a phase change ink having a viscosity of from about 4 mPa's to about 50 mPa's at a first temperature, and having a viscosity of from about 104 mPa's to about 109 mPa's at second temperature, when the second temperature is at least 10° C., but no more than 50° C., below the first temperature.